Epoxy polyester, its emulsion and its preparation as well as water-base coatings containing the emusion

ABSTRACT

The invention discloses an acrylic acid-modified epoxy polyester resin and the preparation process thereof. The resin comprises 100 pbw of a copolymer (A) formed from an unsaturated fatty acid-modified polyester and a bisphenol A type epoxy resin, and 20-40 pbw of poly(meth)acrylic acid (ester) (B). The preparation process comprises the following steps: (1) alcoholyzing a drying oil with a polyol; (2) adding successively, to the product from step (1), a dibasic anhydride, a fatty acid containing a conjugated double bond and an epoxy resin, and esterifying to obtain an epoxy polyester; and (3) copolymerizing the epoxy polyester from step (2) and an acrylic monomer. This invention also provides a water-based emulsion containing said resin, and a water-based paint exhibiting excellent antirust property and having low production cost.

FIELD OF THE INVENTION

[0001] This invention relates to a new polymer, an emulsion containingthe same and preparations thereof, more particularly to an acrylicacid-modified epoxy polyester resin, an emulsion containing the same andpreparations thereof. In addition, this invention relates to awater-based paint comprising said emulsion as a base material,particularly suitable for the anticorrosive coating on a metal surface.

BACKGROUND OF THE INVENTION

[0002] Along with the development of people's consciousness ofenvironment protection, water-based paint is becoming more and morepopular. This is mainly because the water-base paint does not contain anorganic solvent and so is beneficial to the atmosphere and indoorenvironment. Nevertheless, the base material adopted by the existingwater-based paint is mainly conventional emulsion and water-solubleresin. The former contains a large amount of emulsifiers and thewater-proof property of the coating is poor. The latter comprises theacrylic or alkyd resin having a high acid value of 60-90 as a base andthe self-drying property of the coating is poor.

[0003] In order to solve the above-mentioned technical problems, manyefforts have been made. For example, an anticorrosive primer made from awater-based polyurethane-modified alkyd resin is disclosed in a ATpatent No. 8,302,121, which is prepared by reacting acarboxyl-containing and polyether segment-containing acrylicacid-modified alkyd resin (A) and a polyurethane-modified alkyd resin(B) with a diisocyanate in an organic solvent to obtain an acrylicacid-polyurethane-modified alkyd resin, removing the solvent by vacuumdistillation, adding an organic amine to neutralize the carboxyl group,emulsifying with water to obtain an acrylic-polyurethane modified alkydemulsion, which is then mixed with the pigment, filler and aids toobtain an anticorrosive primer, which can be used for anticorrosivecoating steel members. Nevertheless, owing to the presence of thehydrophilic polyether segment in the molecular chain of the resin, thewater-proofness of the coating is poor and thus the anticorrosiveproperty of the coating is adversely affected.

[0004] A water-based acrylic acid anticorrosive paint (Showa Highpolymer Co.) is disclosed in a JP patent No. 03,192,166, which comprisesas a base material an acrylic emulsion made by emulsion polymerizing themonomers including styrene, alkyl (meth)acrylate esters, and glycidylacrylate esters. The anticorrosive paint is mainly used as a pre-coatingprimer and a protective primer in equipment maintenance. Owing to thecorrosion accelerating effect of the ion SO₄ ²⁻ produced by a persulfateinitiator during emulsion polymerization, the problem of flash and backcorrosion occurs. Meanwhile the coating film is more hydrophilic and therust resistance poor.

[0005] A water-based epoxy polyester primer (Dai Nippon Ink Co.) isdisclosed in a JP patent No. 05,306,377, which is prepared by reactingan epoxy resin with a drying oil fatty acid to produce a dryingoil-modified epoxy ester resin, and then reacting the epoxy ester resinwith a carboxy-containing ethylenic monomer and other ethylenicunsaturated monomers to produce a vinyl-modified epoxy resin, thenremoving the solvent by vacuum distillation, neutralizing the carboxygroup by adding an amine, emulsifying with water to form an epoxy esteremulsion, and mixing the resultant emulsion with a pigment, a filler,and an aid to obtain the anticorrosive primer. Owing to a great quantityof organic solvents contained in the intermediate product acrylicacid-modified epoxy ester resin during the synthesis of the resin, atreatment for the removal of the solvent is necessary, which consumes alarge amount of energy and thus makes the production efficiencydecrease.

[0006] Therefore, an object of this invention is to provide a newacrylic acid-modified epoxy polyester resin, which can be prepared froma raw material available easily and has a low cost. The resin can beused to prepare a water-based epoxy polyester emulsion, therebyproducing a cost-effective water-based paint with excellent rustresistance.

[0007] Another object of this invention is to provide a process forpreparing said new acrylic acid-modified epoxy polyester resin. Byadopting said process, said resin can be economically and easilyobtained.

[0008] A further object of this invention is to provide an emulsionproduced from said resin.

[0009] Still a further object of this invention is to provide a processfor preparing said emulsion.

[0010] A further object of this invention is to provide a water-basedpaint comprising the emulsion according to this invention as the basematerial. Said water-based paint has excellent rust resistance and lowproduction cost.

SUMMARY OF THE INVENTION

[0011] For solving the above-mentioned technical problems, the inventorsfound, after researching in a meticulous way, that the objects of thisinvention can be achieved through the following: alcoholyzing a dryingoil and a polyol in the presence of a catalyst; adding successively adibasic anhydride, a unsaturated fatty acid containing a conjugateddouble bond and an epoxy resin and esterifying to obtain an epoxypolyester; and free radical copolymerizing said epoxy polyester andacrylic acid monomer mixtures to obtain an acrylic acid-modified epoxypolyester. Owing to the easy availability of raw materials and lowconcentration of an organic solvent so that the solvent removing step isomitted, the production cost is reduced. In addition, the resultcopolymerization product does not contain a polyether segment, and theacid value of the resin is far lower than that of the commonwater-soluble resin. Furthermore, after neutralized with an amine, saidcopolymerization product self-emulsifies to form a core-shell epoxypolyester emulsion having small particle size and excellenthydrophobicity. When used as a water-based paint, the emulsion can givegood water repellence to the coating.

[0012] Accordingly, this invention provides an acrylic acid-modifiedepoxy polyester resin, composed of 100 pbw of a copolymer (A) made froman unsaturated fatty acid-modified polyester and a bisphenol A typeepoxy resin, and 20-40 pbw of poly(meth)acrylic acid (ester) (B), whichcan be prepared by a process comprising the following steps:

[0013] (1) alcoholyzing a drying oil with a polyol;

[0014] (2) adding successively, to the product from step (1), a dibasicanhydride, a fatty acid containing conjugated double bond and an epoxyresin, and esterifying to obtain an epoxy polyester; and

[0015] (3) copolymerizing the epoxy polyester from step (2) and anacrylic monomer.

[0016] This invention still provides a process for preparing the acrylicacid-modified epoxy polyester resin.

[0017] This invention still provides an epoxy polyester emulsion,comprising 30-50 wt/o of said acrylic acid-modified epoxy polyesterresin.

[0018] This invention still provides a process for preparing said epoxypolyester emulsion, comprising the following steps:

[0019] (1) alcoholyzing a drying oil with a polyol;

[0020] (2) adding successively, to the product from step (1), a dibasicanhydride, a fatty acid containing a conjugated double bond and an epoxyresin, and esterifying to obtain an epoxy polyester;

[0021] (3) copolymerizing the epoxy polyester from step (2) and a(meth)acrylic acid (ester) to obtain an acrylic acid-grafted epoxypolyester resin; and

[0022] (4) neutralizing the product from step (3) with a neutralizer,stirring with water, and self-emulsifying.

[0023] In addition, this invention still provides a water-based paintcomposition, which comprises, based on 100% of the total weight of thecomposition, 20-60 wt % of said acrylic acid-modified epoxy polyesteremulsion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The acrylic acid-modified epoxy polyester resin (R) according tothis invention, the acid value of which is preferably 20-40, composed of100 pbw of a copolymer (A) formed from an unsaturated fattyacid-modified polyester and a bisphenol A type epoxy resin, and 20-40pbw of poly(meth)acrylic acid (ester) (3), can be prepared by a processcomprising the following steps:

[0025] (1) alcoholyzing a drying oil with a polyol;

[0026] (2) adding to the product from step (1) a dibasic anhydride, afatty acid containing a conjugated double bond and an epoxy resin, andesterifying to obtain an epoxy polyester; and

[0027] (3) copolymerizing the epoxy polyester from step (2) and anacrylic monomer.

[0028] In the present invention, a drying oil means an unsaturatedvegetable oil having an iodine value above 130. Preferred drying oilsare selected from a group consisting of linseed oil, dehydrated castoroil and soy bean oil. The drying oil is used at an amount of 30-60 pbw,and preferably 40-50 pbw, based on 100 pbw of (A).

[0029] In the present invention, polyol means a low molecular alcoholcontaining 24 hydroxy groups. Preferred polyols are selected from agroup consisting of glycerin, pentaerythritol and trimethylolpropane.The polyol is used at an amount of 7-18 pbw, and preferably 10-15 pbw,based on 100 pbw of (A).

[0030] The alcoholysis in step (1) of the above preparation process ispreferably conducted at 230-250°C under nitrogen atmosphere in thepresence of a catalyst.

[0031] There are no particular limitations for the dibasic anhydride.Preferred dibasic anhydrides are selected from a group consisting ofphthalic anhydride, tetrahydrophthalic anhydride and maleic anhydride.The dibasic anhydrides are used at an amount of 10-30 pbw, andpreferably 15-25 pbw, based on 100 pbw of (A).

[0032] There are no particular limitations for the fatty acid containinga conjugated double bond. From the viewpoint of a low cost, eleostearicacid is suitably used. The fatty acid containing a conjugated doublebond is used at an amount of 2-10 pbw, and preferably 4-9 pbw., based on100 pbw of (A).

[0033] In the present invention, the epoxy resin means a bisphenol Atype difunctional epoxy resin having a weight average molecular weightof 900-2,000. Among them, epoxy resin E-12, epoxy resin E-20, or themixture thereof are preferred. The epoxy resin is used at amount of20-30 pbw, based on 100 pbw of (A). The resin viscosity is too high whenthe amount used is over 30 pbw. The resin is poor in water resistancewhen the amount used is lower than 20 pbw.

[0034] The esterification in step (2) of the preparation process iscarried out in the presence of a catalyst at 180-220° C., preferably200-220° C. When the acid value reaches 5-10, preferably 6-8, thereaction is completed. The resin is undesirable in water resistance whenthe acid value is greater than 10. The resin viscosity is too high andgelling tends to occur during the reaction when the acid value is lowerthan 5. The reaction between the polyester and the epoxy resin is mainlya reaction between the terminal carboxyl group of the polyester and theterminal epoxy group of the epoxy resin to obtain a straight-chainalternating copolymer.

[0035] The acrylic monomer is preferably one or more of the following:acrylic acid, methacrylic acid, butyl acrylate, butyl methacrylate andmethyl methacrylate. The acrylic monomer is preferably used at an amountof 20-40 pbw based on 100 pbw of (A).

[0036] Under the action of an initiator, the acrylic monomer 1,4- or1,2-co-polymerizes at the conjugated double bond of, for example,eleostearate, to form a copolymerization product comprising acrylate asa side-chain and epoxy polyester as a backbone.

[0037] According to a preferred embodiment of this invention, a processfor preparing the acrylic acid-modified epoxy polyester resin accordingto this invention comprises:

[0038] 1. mixing a drying oil, a polyol and an appropriate amount of acatalyst, heating up to 230-250° C. to alcoholyze, and when the 95%ethanol tolerance becomes 1:9, the alcoholysis is completed;

[0039] 2. adding successively, to the alcoholysate, a dibasic anhydride,an epoxy resin and an eleostearic acid, and ester at 180-220° C. whilemaintaining the temperature, and when the acid value reaches 5-10,preferably 6-8 and the viscosity becomes 4-6 s, the esterification iscompleted. The system is cooled down to below 130° C.;

[0040] 3. dropping in acrylic monomers and an initiator BPO over 1-3 hrsat 100-130°C to conduct a copolymerization, after dropping is complete,the system is allowed to continue to reaction for 3-6 hrs whilemaintaining the temperature.

[0041] The catalysts for both alcoholzing and esterification are metaloxides or hydroxides, preferably PbO and LiOH. The initiator is anorganic peroxide, preferably benzoyl peroxide (BPO).

[0042] When the copolymerization product obtained according to thisinvention is self-emulsified after neutralized with a neutralizer, theepoxy polyester segment in the copolymer is inside the emulsion particleto form a core and the polyacrylate segment is on the surface layer ofthe emulsion particle, which has an electric charge after neutralized,to form a shell. Thus an epoxy polyester emulsion having a core-shellstructure is formed. Because the hydrolysis-resistant polyacrylatesegment in on the shell layer and most of the carboxyl groups are on theshell layer, the self-emulsifying and emulsion stabilizing effects aregood. Compared with the conventional water-soluble resin, the total acidvalue of the resin is greatly reduced, and the water resistance of theacrylic acid-modified epoxy polyester resin is greatly increased.

[0043] A neutralizer and industrial soft water are preferably added intothe epoxy polyester resin prepared according to above-mentioned process,and stirred for 0.5 h to obtain an epoxy polyester emulsion having asolid content of 30-50 wt %.

[0044] The neutralizer is preferably one or more selected from a groupconsisting of 2-amino-1-propanol, N-ethylmorpholine,N,N-dimethyl-ethanolamine and triethylamine.

[0045] The industrial soft water means deionized water or distilledwater, and the content of the water-soluble substances is less than 100ppm, and the conductivity is less than 20 μs/cm.

[0046] The epoxy polyester emulsion according to this inventioncomprises 30-50% of the acrylic acid modified-epoxy polyester resin.

[0047] According to a preferred embodiment of this invention, the epoxypolyester emulsion according to this invention is prepared in accordancewith the following formula: Ingredients pbw Drying oil 30-60 Polyol 7-18 Dibasic anhydride 10-30 Epoxy resin 20-30 Eleostearic acid  2-10Acrylic monomer 20-40 Neutralizer 3-6 Industrial soft water 125-250Catalyst 0.01-0.05 Initiator 0.1-2.0

[0048] The drying oil is an unsaturated vegetable oil having an iodinevalue above 130. Preferred drying oil is one or more selected from agroup consisting of linseed oil, dehydrated castor oil and soy bean oil.The preferred amount of the drying oil is 40-50 pbw.

[0049] The polyol is a low molecular alcohol containing 2-4 hydroxygroups. Preferred polyol is one or more selected from a group consistingof glycerin, pentaerythritol and trimethylolpropane. The preferredamount of the polyol is 10-15 pbw.

[0050] There are no particular limitations for the dibasic anhydride.Preferred dibasic anhydride is one or more selected from a groupconsisting of phthalic anhydride, tetrahydrophtalic anhydride and maleicanhydride. The preferred amount of the dibasic anhydride is 15-25 pbw.

[0051] The epoxy resin is a bisphenol A type difunctional epoxy resinhaving a weight average molecular weight of 900-2,000. The amount usedof the epoxy resin is 20-30 pbw. The resin viscosity is too high whenthe amount used is greater than 30 pbw. The resin is poor in waterresistance when the amount used is lower than 20 pbw.

[0052] The acrylic monomer is preferably one or more selected from agroup consisting of acrylic acid, methacrylic acid, butyl acrylate,butyl methacrylate and methyl methacrylate.

[0053] The neutralizer is preferably one or more selected from a groupconsisting of 2-amino-1-propanol, N-ethylmorpholine,N,N-dimethyl-ethanolamine and triethylamine.

[0054] The industrial soft water is deionized water or distilled water,and the content of the water-soluble substances is less than 100 ppm,and the conductivity is less than 20 μs/cm.

[0055] The catalyst is metal oxides or hydroxides, preferably PbO andLiOH. The initiator is an organic peroxide, preferably benzoyl peroxide(BPO).

[0056] The epoxy polyester emulsion according to this invention is usedas the base material to produce a water-based paint, comprising:Ingredients wt % Epoxy polyester emulsion 20-60 Inert antirust pigment 5-30 Active antirust pigment  1-10 Filler  5-30 Drier 1-5 Thickener0.2-5   Aids 0.5-2.5 Industrial soft water  5-10

[0057] The water-based paint can be prepared by a conventional method inthe art, for example, a preparation process comprising the followingsteps:

[0058] (1) in a vessel, metering the industrial soft water and aids, andmixing well with an adjustable high speed dispersion machine (the samebelow);

[0059] (2) adding more than half the amount of the epoxy polyesteremulsion, and mixing well;

[0060] (3) adding an inert antirust pigment, an active antirust pigmentand a filler, and mixing well;

[0061] (4) grinding with a ball mill or a sand mill until a fineness isless than 50 μm to obtain a colored sly;

[0062] (5) in a paint mixer, adding said colored slurry, the remainingepoxy polyester emulsion and a drier, and mixing well; and

[0063] (6) adding a thickener, mixing well, and filtering to obtain thefinal product.

[0064] The epoxy polyester emulsion is prepared by the above-mentionedprocess, with a solid content of 30-50 wt %. The preferred amount ofsaid emulsion in the paint is 40-50 wt %.

[0065] There are no particular limitations for the inert antirustpigment. Any inert antirust pigment can be used provided that it doesnot react with the ingredients in said water-based paint composition.The inert antirust pigment is preferably one or more selected from agroup consisting of iron oxide red and mica-iron oxide. The preferredamount of the inert antirust pigment in the paint is 10-25 wt %.

[0066] There are no particular limitations for the active antirustpigment. Preferred are one or more selected from a group consisting ofZn₃(PO₄)₂, ZnMoO₄, zinc chrome yellow, strontium chrome yellow, aluminumtriphosphate, basic lead chromate/silicate and barium metaborate. Thepreferred amount of the active antirust pigment in the paint is 2-5 wt%.

[0067] The filler is preferably one or more selected from a groupconsisting of talc powder, mica powder, natural barite powder, calcitepowder, light calcium carbonate, precipitated barium sulfate andcalcined kaolin. The preferred amount of the filler in the paint is10-20 wt %. The content of the water-soluble substances in the inertantirust pigment and the filler should be<0.5 Wt %, and preferably <0.3Wt %.

[0068] The thickener is an alkali-soluble acrylic acid emulsionthickener, and the preferred amount of the thickener in the paint is0.5-2.0 wt %.

[0069] The drier is an emulsion comprising cobalt naphthenate, manganesenaphthenate and zinc naphthenate as active ingredients and the preferredamount of the drier in the paint is 1-3 wt %.

[0070] The industrial soft water is deionized water or distilled water,in which the total amount of water-soluble substances is <100 ppm, andthe conductivity is <20 μs/cm.

[0071] The aids are any conventionally used ones in the art, forexample, a dispersing agent, a wetting agent, a defoamer, antiseptics,antifungal and neutralizer.

[0072] The dispersing agent can be one or more selected from the groupconsisting of sodium salt, ammonium salt and amine salt, of a copolymerformed from an ethylenic monomer and an unsaturated fatty acid andesters thereof.

[0073] There are no particular limitations for the wetting agent.Preferred is polyether-modified acetylenic alcohol. The defoamer is apolyether-modified organic silicone. The neuter is a volatile organicamine. Preferred neutralizers are one or more selected from a groupconsisting of monoethanolamine, 2-amino-1-propanol, N-ethylmorpholine,triethylamine and N,N-dimethylethanolamine.

[0074] The following is the examples of this invention. It is to beunderstood that the invention is not limited to these examples.

[0075] Table 1 shows the examples for the emulsion synthesis andperformance parameters of the resultant emulsion, in which E-12 and E-20are bisphenol A type epoxy resin manufactured by Yixing Resin Plant,Jiangsu province, China; AMP-95 is 2-amino-1-propanol manufactured byAir Products and Chemicals Inc., U.S.A. Table 2 shows the example forthe water-based paint, in which resin 1, resin 2 and resin 3 are formedrespectively from example 1, 2 and 3 in Table 1. Drier VXW is a productfrom Vianova co., Austria. Thickener TT935 is a product fromDongfang-Rome&Hass Co., Beijing. The dispersing agent 5040 and 5027 anddefoamer NXZ are products from Henckel AG, Germany. The wetting agentSURFYNOL GA is a product from Air Products and Chemicals Inc., U.S.A.Table 3 shows the performance parameters of the water-based paint in theexamples in Table 2.

[0076] The methods for measuring and evaluating various performances, inthese examples, are as follows: GB6753.3-86 thermal stability GB1728-89drying time GB9268-88 freeze-thaw stability GB1720-79 adhesive forceGB6753.3-86 mechanical stability GB/T1732-93 impact resistance GB/T1733-93 waterproof-ness GB/T1731-93 flexibility (dry film) GB9753-88cupping test GB6753.3-86 paint appearance GB/T1771-91 salt fogresistance GB1724-89 fineness GB 9268-88 freeze-thaw GB1724-89 viscosityresistance GB6751-86 solid content

[0077] In addition, the method for plating in measuring the coatingperformance in the examples is as follows:

[0078] Plating according to GB 1727-92, in which the tinned plate isused for adhesive force, impact resistance, flexibility, and cupping.The plate is brush coated for two times till a film thickness of 20-30μm is obtained. The low-carbon steel plate is used for salt fogresistance. The low-carbon steel plate is scrubbed with acetone toremove the oil, sanded, and spray coated for two times till a filmthickness of 70-110 μm is obtained. Then, the sample plate is dried for14 days at 23+2° C.

[0079] 1. Preparing Examples for Epoxy Polyester Emulsion

EXAMPLE 1

[0080] In reactor 1, adding 400 g of linseed oil, 90 g of glycerin and0.2 g of LiOH. Heating up to 230-240° C. and maintain the temperaturefor 1.5 h. When the tolerance of 95% ethanol becomes 1:9, cooling downto 180° C. Adding 200 g of phthalic anhydride, 50 g of eleostearic acidand 50 g of reflux xylene. Maintain the temperature at 180-190° C. for 3hrs. 20 g of reflux xylene is removed and 260 g of epoxy resin E-12 isadded. The temperature is raised up to 210-220°C. and maintained for 2hrs until the acid value of the resin dropped to 7.8. The system iscooled down to below 150° C. and transferred to reactor 2, where a mixedsolution composed of 20 g of methacrylic acid, 10 g of acrylic acid, 110g of methyl methacrylate, 110 g of butyl acrylate, 30 g of n-butanol and5 g of benzoyl peroxide (BPO), was dropped in over 3 hrs at 100-110° C.The reaction is continued for 3 hrs while maintaining the temperatureuntil the acid value of the resin reached 30. The resin is transferredfrom reactor 2 to reactor 3. The residual monomer was removed during thetransferring. 55 g of neutralizer AMP-95 and 1,400 g of industrial softwater were added into reactor 3, adding, and the resultant mire wasstirred for 0.5 h to obtain epoxy polyester emulsion 1.

EXAMPLES 2-5

[0081] Repeat the procedures in Example 1 except that the raw materialand amounts thereof are shown in Table 1 in order to obtain variousresins. TABLE 1 Examples for emulsion synthesis (unit: pbw) Example Item1 2 3 4 5 Linseed oil 40 50 60 0 50 Soy bean oil 0 0 0 50 0 glycerine 98 7 8 8 phthalic anhydride 20 15 10 15 15 Epoxy resin E-12 26 23 20 23 0Epoxy resin E-20 0 0 0 0 23 eleostearic acid 5 4 3 4 4 methacrylic acid2 2 2 2 2 acrylic acid 1 1 1 1 1 methyl methacrylate 11 11 11 9 13 butylacrylate 11 11 11 13 9 industrial soft water 140 150 130 160 170 AMP-955.5 5 4 5 4.5 self-emulsifying property good good good good good thermalstability good good good good good water tolerance(film) 48 48 48 48 48freeze-thaw stability 5 5 5 5 5 mechanical stability excellent excellentexcellent excellent excellent

[0082] 2. Preparation of a Water-Based Paint

EXAMPLE 6

[0083] In a vessel, 95 g of industrial soft water, 1.0 g of wettingagent SURFYNOL GA, 1.5 g of dispersant 5040, 0.1 g of defoamer NXZ, 2.5g of antiseptics KATHON LXE (Rome & Hass Co. U.S.A), 2.6 g of antifingalSKANE M-8 (Rome & Hass Co. U.S.A.), 3 g of 2-amino-1-propanol (AMP-95),are added and mixed well. 300 g of the epoxy polyester emulsion preparedfrom example 1 is added and mixed well. 220 g of iron oxide red, 80 g ofmica powder (600 mesh), 100 g of precipitated BaSO₄, 15 g of Zn₃(PO₄)₂,and 5 g of ZnMoO₄ are added and mixed well. The resulting mixture isgrinded with a sand mill until a fineness of <50 μm is obtained to forma colored slurry. The resultant colored slurry is added into a paintmixer, and 150 g of the epoxy polyester emulsion prepared from example1, 15 g of drier VXW, 10 g of thickener TT-935 and 3 g of2-amino-1-propanol (AMP-95) are added, mixed well, and filtered toobtain the final product.

EXAMPLES 7-14

[0084] The process for preparing the water-based paint of example 7-14is the same as that in Example 6 except that the raw materials used areshown in 2#-9# in Table 2. TABLE 2 Examples for water-based paint (unit:g) Example raw material (g) 1# 2# 3# 4# 5# 6# 7# 8# 9# soft water 95 6050 95 70 50 70 60 55 SORFYNOL GA 1.0 1.5 1.5 1.8 1.5 1.6 1.1 1.4 1.2dispersant 5040 1.5 1.6 1.4 1.7 1.0 1.6 0 0 0 dispersant 5027 0 0 0 0 00 1.5 1.7 1.3 defoamer NXZ 0.1 0.2 0.3 0.3 0.2 0.2 0.1 0.2 0.1 KATHONLXE 2.5 1.1 1.5 2.6 2.8 1.2 2.2 1.3 2.7 SKANE M-8 2.6 1.2 1.0 2.3 2.22.0 1.8 1.3 2.4 AMP-95 6 4 3 2 2.5 3 4 6 5 iron oxide red 220 190 0 0 00 250 190 200 Mica iron oxide 0 0 250 200 190 200 0 0 0 800 mesh talc 0105 70 100 80 60 60 50 0 600 mesh mica 80 0 0 0 60 65 0 100 80 ppt.BaSO₄ 100 100 0 100 100 50 0 50 100 calc. kaolin 0 0 80 0 0 0 120 50 0Zn₃(PO₄)₂ 15 10 10 10 15 35 10 5 20 ZnMoO₄ 5 5 10 10 5 10 5 5 5 Resin 1450 500 500 0 0 0 0 0 0 Resin 2 0 0 0 450 450 500 0 0 0 Resin 3 0 0 0 00 0 450 450 500 VXW drier 15 16 17 17 18 19 18 19 20 TT935 thickener 109 8 10 9 8 10 9 8

[0085] TABLE 3 Performances for water-based paint Example Item 1 2 3 4 56 7 8 9 Paint appearance accepted accepted accepted accepted acceptedaccepted accepted accepted accepted coating appearance accepted acceptedaccepted accepted accepted accepted accepted accepted accepted fineness,μm 45 45 45 45 45 45 45 45 45 viscosity, s, > 30 30 30 30 30 30 30 30 30solid content, %, > 50 50 50 50 50 50 50 50 50 drying surface 2 2 2 2 22 2 2 2 time dry, h real dry, h 24 24 24 24 24 24 24 24 24 adhesiveforce, 1 1 1 1 1 1 1 1 1 degree impact resistance, 40 40 40 40 40 40 4040 40 Kg · cm flexibility, mm 2 2 2 2 2 2 2 2 2 cupping, mm 5 5 5 5 5 55 5 5 Salt fog tost, h 500 500 500 500 500 500 500 500 500 freeze-thawtest, 5 5 5 5 5 5 5 5 5 cycle

[0086] Compared with the existing water-based acrylic acid, water-basedepoxy polyester and water-based alkyd antirust paint, the epoxypolyester emulsion according to this invention and the water-based paintcomprising said emulsion as the base material have a lot of advantages.Firstly, the antirust property is good, which is because of followingreasons: (1) the present water-based paint comprises the emulsifier-freeepoxy polyester emulsion as the base material and the emulsion does notcontain polyether segment, and also the acid value of the resin is farlower than the common water-soluble resin and the hydrophobicity of thepaint film is good; (2) the emulsion particles have a small particlesize (130 nm) and are narrowly distributed, and thus the paint film hashigh denseness; (3) because no persulfate initiator is used during thesynthesis of the resin, sulfonic group or SO₄ ²⁻ ion having a corrosionaccelerating effect is not produced; and (4) in addition, the mechanicalstability of said epoxy polyester emulsion is good. The emulsion can beground together with a pigment and filler, and so the amounts of thehydrophilic dispersant and wetting agent can be greatly reduced. Thewater resistance of the paint film is further improved. Hence, theantirust property of the coating of the water-based paint according tothis invention is obviously superior to the water-based primercomprising the common acrylic emulsion, water-soluble acrylic resin orwater-soluble alkyd resin as the base material. Secondly, the stabilityis good. The epoxy polyester emulsion according to this invention has arelatively high thermal stability. The inert pigment iron oxide red isused as the main antirust pigment in the present water-based paint, andso both the storage stability and the freeze-thaw stability of the paintare good. Thirdly, it is easy and safe to use the water-based paintaccording to this invention. The water-based paint according to thisinvention does not contain a cosolvent can be directly diluted withwater. The paint according to this invention is characterized innon-toxicity, incombustibility, quick-drying, safety and easy inoperation, and high-efficiency. It has been proved that said water-basedpaint is suitable for anticorrosive metal paints in the facilities suchas train, automobile, ship, bridge, pipeline and storage tanks.Fourthly, said water-based paint can be prepared from a wide variety ofraw materials, has a low cost, and is easy to apply on a large scale.

[0087] The specification and examples above are presented to aid in thecomplete and non-limiting understanding of the invention disclosedherein. Since many variations and embodiments of the invention can bemade without departing from its spirit and scope, the invention residesin the claims hereinafter appended.

What is claimed is:
 1. An acrylic acid-modified epoxy polyester resin,comprising 100 pbw of a copolymer (A) made from an unsaturated fattyacid-modified polyester and bisphenol A type epoxy resin, and 20-40 pbwof poly(meth)acrylic acid (ester) (B), which can be prepared by aprocess comprising the following steps: (1) alcoholyzing a drying oilwith a polyol; (2) adding successively, to the product from step (1), adibasic anhydride, an unsaturated fatty acid containing a conjugateddouble bond and an epoxy resin, and esterifying to obtain an epoxypolyester; and (3) copolymerizing the epoxy polyester from step (2) andan acrylic monomer.
 2. An acrylic acid-modified epoxy polyester resinaccording to claim 1, having an acid value of 20-40.
 3. An acrylicacid-modified epoxy polyester resin according to claim 1, wherein saiddrying oil is an unsaturated vegetable oil having an iodine value above130.
 4. An acrylic acid-modified epoxy polyester resin according toclaim 1, wherein said polyol is selected from the group consisting ofglycerine pentaerythritol, trimethylolpropane, or the mixture thereof,and the amount of said polyol, based on 100 pbw of (A), is 10-15 pbw. 5.An acrylic acid-modified epoxy polyester resin according to claim 1,wherein said dibasic anhydride is selected from the group consisting ofphthalic anhydride, tetrahydrophthalic anhydride, maleic anhydride, orthe mixture thereof, and the amount of said dibasic anhydride, based on100 pbw of (A), is 15-25 pbw.
 6. An acrylic acid-modified epoxypolyester resin according to claim 1, wherein said epoxy resin is abisphenol A type difunctional epoxy resin having a weight averagemolecular weight of 900-2,000, and the amount of the resin, based on 100pbw of (A), is 20-30 pbw.
 7. An acrylic acid-modified epoxy polyesterresin according to claim 1, wherein said unsaturated fatty acidcontaining a conjugated bond is preferably eleostearic acid, and theamount of the unsaturated fatty acid, based on 100 pbw of (A), is 2-10pbw.
 8. An acrylic acid-modified epoxy polyester resin according toclaim 1, wherein said acrylic monomer is one or more selected from thegroup consisting of acrylic acid, methacrylic acid, butyl acrylate,butyl methacrylate and methyl methacrylate, and the amount of theacrylic monomer, based on 100 pbw of (A), is 20-40 pbw.
 9. An acrylicacid-modified epoxy polyester resin according to claim 1, wherein saidesterification in step (2) of said process is carried out at 180-220°C., and when the acid value is 5-10, preferably 6-8, and the viscosityis 4-6 s, the esterification is complete.
 10. A process for preparingthe acrylic acid-modified epoxy polyester resin according to any one ofclaims 1-9, comprising the following steps: (1) alcoholzing a drying oilwith a polyol; (2) adding successively, to the product from step (1), adibasic anhydride, an unsaturated fatty acid containing a conjugateddouble bond and an epoxy resin, and esterifying to obtain an epoxypolyester; and (3) copolymerizing the epoxy polyester from step (2) anda (meth)acrylic acid (ester).
 11. An epoxy polyester emulsion comprising30-50 wt % of said acrylic acid-modified epoxy polyester resin accordingto any one of claims 1-9.
 12. A process for preparing the epoxypolyester emulsion according to claim 11, comprising the followingsteps: (1) alcoholyzing a drying oil with a polyol; (2) addingsuccessively, to the product from step (1), a dibasic anhydride, anunsaturated fatty acid containing a conjugated double bond and an epoxyresin, and esterifying to obtain an epoxy polyester; (3) copolymerizingthe epoxy polyester from step (2) and a (meth)acrylic acid (ester); and(4) neutralizing the product from step (3) with a neutralizer, stingwith water, and self-emulsifying.
 13. A water-based paint compositioncomprising, based on 100% of total weight of the composition, 20-60 wt %of the acrylic acid-modified epoxy polyester emulsion according to claim11.